The Food and Drug Administration has framed its two-day meeting as a "scientific, technologic and clinical" discussion about how to test the approach in humans. But the technique itself raises a number of ethical questions, including whether the government should sanction the creation of genetically modified humans.

The FDA panel will hear from several prominent critics who oppose any human testing of the approach, arguing that it could be a slippery slope toward "designer babies," - in which parents customize traits like eye color, height and intelligence.